1. Field of the Invention
The present invention relates to a noise canceling technique when an image sensing apparatus records a sound along with an image sensing operation.
2. Description of the Related Art
Recent image sensing apparatuses such as a digital camera are gaining more sophisticated functions. Some image sensing apparatuses can sense moving and still images. When sensing a moving image, a sound is recorded at the same time as sensing images of the moving image, and the images and sound are recorded as one data. At this time, it is desirable to acquire a sound generated by an object so that it can be actually perceived by the human auditory perception. However, the sound is affected by noise such as driving noise of the apparatus that is generated inside the image sensing apparatus in recording. To reduce the influence of noise in sound recording, various image sensing apparatuses have been proposed.
Japanese Patent Laid-Open No. 2005-130328 discloses a technique of removing the frequency band of noise from a sound signal recorded via the microphone of an image sensing apparatus. This technique adopts a bandpass filter which cuts off the frequency band of noise generated by a noise source inside the image sensing apparatus.
Japanese Patent Laid-Open No. 2005-244613 discloses a technique using a noise microphone arranged inside an image sensing apparatus, in addition to an object microphone. In this technique, filters are applied to signals output from the respective microphones so as to cancel out only sound signals having noise components when these output signals are added.
The effect of cutting off the frequency band of noise, like Japanese Patent Laid-Open No. 2005-130328, can be expected when the frequency band of a noise signal is narrow. However, if the frequency band of a noise signal is wide, even the frequency band of a sound generated by an object may be cut off.
When filters are applied to respective sound sources, like Japanese Patent Laid-Open No. 2005-244613, it is important whether the filters are appropriately modeled for sounds generated by the noise source and object. If the property of the noise source changes as in a lens-interchangeable camera or the like, it is difficult to model the filter for the noise source in advance, and satisfactory noise reduction may not be expected. Especially in Japanese Patent Laid-Open No. 2005-244613, the microphone is arranged to acquire noise from the noise source in the image sensing apparatus. However, the noise source may be moved within the image sensing apparatus. As the noise source moves, the frequency characteristic of a signal output from the noise microphone also changes. This makes it more difficult to model the filter for the noise source, and noise may not be properly reduced.